Mary Portman (Naomi Watts) is a child psychologist in the hinterland of Maine. A car crash has left her a widow and left her step-son Stephen (Charlie Heaton) bedridden and dependent on special care. One day one of Mary's young patients disappears, setting the psychologist to his rescue before a powerful snowstorm makes it impossible to find him alive. But the bad weather seems to involve the house in mystery as apparitions of what may be the ghost of the lost boy haunt Mary and her step-son.